We propose to study the effects of ethanol on isolated ganglia from Aplysia californica maintained in vitro. The primary goal is to establish tolerance and study its mechanism. The preparation was chosen because it is favorable for prolonged neurophysiological studies and because it can be maintained in culture for several weeks so that it can be used for chronic drug studies. We will first study acute effects of this drug in graded series of concentrations on a number of neurophysio- logical parameters, concentrating on effects on synaptic transmission (including miniature synaptic potentials) at an identified synapse which is presumed to be cholinergic. The EPSP recorded from this synapse is unitary, monosynaptic and shows a range of plasticities (depression, frequency facilitation, post-tetanic potentiation) each of which might be affected by ethanol administration. By maintaining isolated portions of the central nervous system in organ culture, for periods up to weeks, chronic effects of ethanol will be studied in an attempt to determine if tolerance to some action can be established and if signs of "withdrawal" occur upon removal of the drug from the medium. Should tolerance and withdrawal develop, we will attempt to determine the mechanism of this alteration using neurophysiological and biochemical techniques.